Japanese Patent Application Publication No. 2005-330108 discloses a sheet post-processing apparatus for performing processes such as stitching and folding.
The apparatus includes a sheet stack for stacking sheets for automatic stapling and at least one finger attached movably on the mount for specifying the main surface in contact with the uppermost sheet on the sheet stack in parallel. As the sheets on the stack are increased, to permit the finger to keep continuously in contact with the sheets in parallel, the mount can move for the stack. The weight of the finger prevents the sheets in the receiving tray from being bent and curved.
However, in the apparatus aforementioned, the finger is kept continuously in contact with the sheets in parallel by it own weight and the sheet stack is structured so as to stack sideways the sheets. Therefore, the apparatus cannot respond to the bending and curling of the lower ends of the sheets supported in a standing position.
Further, a problem arises that in addition to the means for driving the stack belt for promoting stacking of sheets, a motor and a solenoid for moving the finger are necessary separately.